1. Field of the Invention
This invention relates to protecting foamed plastic materials from damage due to abrasion and impact, and more particularly to providing abrasion resistance, high gloss and lubricity to decorated and/or printed foamed plastic articles.
Plastic articles such as disposable cups, bowls and labels, particularly those made from foamed thermoplastic resins such as polystyrene and the like, are widely used because of their thermal resistance to hot and cold beverages, high strength to weight ratios, and economics. Also, such materials are extensively used in the packaging industry for labeling containers such as glass bottles and jars where individual partitions may be eliminated on shipping. In many of the above applications, the exterior surfaces of the foamed plastic material are decorated and/or printed, and must be able to withstand considerable surface-to-surface abrasion without scuffing, marring or other objectionable damage. Also, such surfaces must provide suitable lubricity to allow sliding contact with each other, as well as the surfaces of filling and capping equipment on further handling of the containers. The inherent nature of the foamed plastic material varies due to its cellular structure, and especially when the material is oriented to be heat-shrunk in place on containers or fabrication mandrels. The cells tend to open or weaken which leaves the base material particularly susceptible to abrasion damage.
Foamed plastic articles, made from thermoplastic resins which are fabricated into cups, bowls and labels, are frequently relatively rigid or semi-rigid and, therefore, tend to abrade when subjected to even moderate sliding contact. In most of the above applications, the exterior surfaces of the articles are decorated or printed with desired advertising images or informational messages while in the form of roll stock from which suitable blanks are made. When the articles are fabricated into cups or bowls, or tubular sleeves to be used as labels on glass bottles or jars, the exterior surfaces must be capable of withstanding both impact and abrasion forces without damage. In instances where the materials are used as labels, and also serve as partitions between containers where long shipments are required, the labels can and do exhibit serious scuffing and abrasion damage to the decorative or printed images, thus detracting from their marketability.
2. Description of Prior Art
Many of the most common uses of foamed plastic material as stated have not employed a protective overcoat for the plastic substrate and thus have incurred deleterious surface damage, especially where long shipments of containers are required. The existing types of clear, transparent coatings are either too expensive or too limited in their properties for widespread commercial use. The commercially available materials are generally organic-solvent based which tend to contaminate the atmosphere on drying. Further, they do not provide abrasion resistance for long distance shipping of such containers.